Disposable absorbent articles generally contain absorbent fibrous webs, such as airlaid or bonded carded webs. Such webs are often stabilized with binder fibers during web formation. More specifically, the binder fibers are normally multicomponent fibers with a significant difference, i.e. at least 20° C., in melt temperature between the higher-melting and the lower-melting components. The fibers are thus heated at a temperature sufficient to melt the lower-melting components, but not the higher melting components. Several binder fibers have been developed that are biodegradable to enhance the disposability of the absorbent article. Many commercially-available biodegradable polymers are formed from aliphatic polyester materials. Although fibers prepared from aliphatic polyesters are known, problems have been encountered with their use. For example, aliphatic polyesters have a relatively slow crystallization rate in comparison to polyolefin polymers, thereby often resulting in poor processability. Most aliphatic polyesters also have much lower melting temperatures than polyolefins and are difficult to sufficiently cool following thermal processing. In addition, many aliphatic polyesters (e.g., poly(lactic acid)) undergo severe heat-shrinkage due to the relaxation of the polymer chain during downstream heat treatment processes, such as thermal bonding and lamination. Thus, biodegradable binder fibers were developed in response to these and other problems. One such binder fiber is described in U.S. Pat. No. 6,177,193 to Tsai, et al. The binder fiber of Tsai, et al. is formed from two components, one of which is a blend of an aliphatic polyester, multicarboxylic acid, and wetting agent. The multicarboxylic acid is required to reduce the viscosity of the polymer for processing, as well as to facilitate crystallization (i.e., nucleating agent) during quenching. One problem with such fibers, however, is that they require a manufacturing process that is relatively complex and inefficient. In addition, the fibers are also weak and have a relatively low tensile strength.
As such, a need currently exists for a fiber that is biodegradable and easily processed into fibrous structures that exhibit good mechanical properties.